In U.S. Pat. Nos. 3,347,454; 3,672,564; and 3,719,406, centrifuges are disclosed utilizing collapsible centrifuge bags for the continuous washing of blood cells positioned in the bags during the centrifuge operation. To provide a continuous connection with the exterior while the centrifuge is rotating, a rotary seal distributor member is disclosed including an apertured spindle coaxially mounted in a housing and projecting from its end, with several spaced ring seals positioned about the spindle. The annular spaces which are defined by the ring seals serve as separate chambers through which fluid flows either into or out of the system. For example, two separate washing systems may be routed through the same rotary seal structure, as illustrated in the last-cited patent.
The flexible, collapsible centrifuge bags are particularly desirable for washing blood and separating blood components, since they can be collapsed flat by suction to completely empty without the use of an excess of washing solution to remove the blood cells.
It is of course desirable for the bags to be manufacturable in the most economical and efficient manner possible, which generally is to manufacture them in flat configuration by heat sealing a pair of sheets of plasticized polyvinylchloride or other appropriate plastic together at their periphery to define the bag. At the same time, when the bag is expanded in the centrifuge cup, it is desirable for a minimum of wrinkles to be present in the bag, which wrinkles tend to retain the blood cells and interfere with washing and separation process.
Also, it is desirable to provide means to prevent the radially outwardly collapse of the flexible collapsible container utilized herein, so that the containers do not crush down into the centrifuge cup upon centrifugation.
It is also desirable to utilize a collapsible centrifuge bag which can also serve as a blood bag for administration of its contents to a patient, so that a transfer of the contents from the centrifuge bag to a separate blood bag is unnecessary.